21021316 has 12 divisors (see below), whose sum is σ = 38951388. Its totient is φ = 9892352.

The previous prime is 21021293. The next prime is 21021323. The reversal of 21021316 is 61312012.

It can be written as a sum of positive squares in 2 ways, for example, as 19766916 + 1254400 = 4446^2 + 1120^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 21021316.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 154501 + ... + 154636.

It is an arithmetic number, because the mean of its divisors is an integer number (3245949).

Almost surely, 2^21021316 is an apocalyptic number.

It is an amenable number.

21021316 is a deficient number, since it is larger than the sum of its proper divisors (17930072).

21021316 is a wasteful number, since it uses less digits than its factorization.

21021316 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 309158 (or 309156 counting only the distinct ones).

The product of its (nonzero) digits is 72, while the sum is 16.

The square root of 21021316 is about 4584.9008713384. The cubic root of 21021316 is about 275.9857340522.

Adding to 21021316 its reverse (61312012), we get a palindrome (82333328).

The spelling of 21021316 in words is "twenty-one million, twenty-one thousand, three hundred sixteen".